For the production of a 2-[6-(hydroxymethyl)-1,3-dioxan-4-yl]acetic acid derivative, the following processes are known.    (1) A process starting with 3-hydroxy-γ-butyrolactone to synthesize a 3,5,6-trihydroxyhexanoic acid ester derivative via a 3,5-dihydroxyhexanoic acid ester derivative (Japanese Kokai Publication Hei-4-173767).    (2) A process starting with 3,4-dihydroxybutyronitrile acetonide to synthesize a 3,5,6-trihydroxyhexanoic acid ester derivative via a 3,5-dihydroxyhexanoic acid ester derivative (Japanese Kokai Publication Hei-2-262537).    (3) A process starting with a 4-chloroacetoacetic acid ester to synthesize a 3,5,6-trihydroxyhexanoic acid ester derivative via conversion to a benzyloxy derivative, reduction and chain extension (Japanese Kokai Publication Hei-6-65226).    (4) A process starting with a 4-chloro-3-hydroxybutyric acid ester to synthesize a 3,5,6-trihydroxyhexanoic acid ester derivative through chain extension, reduction, etc. (U.S. Pat. No. 5,278,313).    (5) A process starting with malic acid to synthesize a 3,5,6-trihydroxyhexanoic acid ester via a 2,4-dihydroxyadipic acid derivative (Japanese Kokai Publication Hei-4-69355).
However, those processes involve reactions at a super-low temperature in the neighborhood of −80° C. (1, 2, 4, 5) or a hydrogenation reaction at a high pressure of 100 kg/cm2 (3), thus requiring the use of special reaction equipment. Moreover, the processes involve the use of costly reagents in some stage or other and, therefore, none of them is an efficient process for commercial-scale production.
The prior art process (4), for instance, comprises reacting a 4-chloro-3-hydroxybutyric acid ester with an enolate of tert-butyl acetate using costly lithium hexamethyl disylazide at a super-low temperature of −78° C. in the first step and performing a stereoselective reduction using costly diethylmethoxyborane and sodium borohydride, again at a super-low temperature of −78° C., in the second step. This process further involves an acetoxylation reaction with costly tetra-n-butylammonium acetate in the costly solvent 1-methyl-2-pyrrolidinone.